What condition were the plugs in? Any worse than the rest?

Monitor what the O2 sensors, fuel pressure, and injector trim are. Should somewhat clue you in if it is lean or rich.

What wires did you change out? These should be coil on plug????

 

Plugs were normal wear. Replaced all plugs, spark plugs wires, coils and fuel injectors. All new. All had no visible signs of damage or burns. It has 100,000 miles.

 

ACdelco/gm plugs?

 

Yes.... and we tried two different sets.

 

These vehicles don't have spark plug wires. Can't be a 2011. Take a picture of the car and post it. The injectors are a ***** to change as well.

 

These vehicles don't have spark plug wires. Can't be a 2011.

Exactly why I was asking about wires. I think only the 3.4L in the previous gen had wires. But....the Terrain didn't exist then. That would be an Equinox or Torrent. The Terrain should be a 2.4 or a 3.0 as a 2011 which "should" be coil on plug.

 

My mechanic has the car.. we replaced everything. At a total loss.... I need this car....trying to figure out what is causing the problem. We have eliminated everything.

 

Check for vacuum leaks around the intake manifold.
Check fuel pressure. Fuel pressure should be at specification.

 

Ask the mechanic, when they replaced the rear plugs if there were oil on them. The valve cover gaskets and spark plug tube seals can leak, fill the tub with oil and will cause a misfire. Otherwise, you will need a mechanic with a VERY GOOD scanner that can run a PICO scope on it and look at the firing order and monitor fuel trims, etc. If he can't do that find another mechanic. Where do you live?